The present invention generally relates to a simulation method, in particular, a fault diagnosis based on a model having a structure and an operation of an object apparatus.
Conventional model-based reasoning and fault diagnosis are executed on the basis of a model which describes a structure and operations of the parts of an apparatus which is an object of the reasoning and fault diagnosis as is described in "Randall Davis, Walter Hamscher, Model-based Reasoning: Troubleshooting, Exploring Artificial Intelligence, pp. 297-346 (1988)".
In such a model, the relationship of a normal value between input terminals Ail, . . . , Aim of a part A and output terminals Aol, . . . , Aon thereof in a normal condition is described as the operation of the part using a function FA, like "(Aol, . . . , Aon)=FA (Ail, . . . , Aim)"and the connective relationship between the output terminal Aox of the part A and the input terminal Biy of a part B is described as the structure of the apparatus using a predicate "connect" like "connect (Aox, Biy)".
In fault diagnosis, the cause of a fault is located using a symptom on the basis of the following criteria.
That is, if the value of the output terminal is abnormal,
(1) either of the values of the input terminals is abnormal, or
(2) the part has failed (alternatively, the operation model of the part is wrong).
However, in the aforementioned model, since each of the parts of the apparatus is defined as that having an independent operation, only a device, such as an electric circuit in which parts thereof are connected with each other via signal lines can be an object of inference or fault diagnosis.